BSCI 124 extra-credit project:

1) Please pick up your plant kit bag

2) Fill out Entry Ballot (yellow paper) to enter textbook raffle… Fold andplace ballot in the box.

ENTRY BALLOTBSCI 124

Name: ______________Major: ______________

Reason for taking this class:

What do you want to getout of this class?

Do you have any special Interst in plant biology?

BSCI 124: LECTURE 2

THE AMAZING PLANT CELLTHE AMAZING PLANT CELL

Prof. Edgar Moctezuma, Ph.D.Prof. Edgar Moctezuma, Ph.D.

TODAY…• Pick up: Your free Plant Project Kit & fill ballot

• Life’s molecules: – Carbohydrates– Lipids– Proteins – Nucleic acids

Raffle: borrow a Textbook for free!• What is a cell? • The Cell Theory• Cell components: cell wall, organelles• Endosymbiont Theory

Cell Macromolecules:The Molecules of Life

The cell is made of the following four biologically important molecules:

• Carbohydrates (sugars, starches, cellulose)

• Lipids (fats, oils, waxes, phospholipids, steroids)

• Proteins (composed of amino acids)

• Nucleic Acids (DNA, RNA)

Life’s molecules• All life’s molecules share the following four

characteristics:

1. Carbon-based

2. Formed from a few elements: C, H, O, N, P

3. Modular construction (like bricks, cheap and easy to build small building blocks)

4. Their function depends on structure(or, structure/shape determines function)

Why should we learn about life’s molecules?

• Because we eat them everyday!

• We are composed of these bio-molecules

1. Carbohydrates• Organic molecules composed of C, H, O

(1:2:1 ratio)

• Most abundant of life’s molecules

CarbohydratesThere are three types of carbohydrates:

Mono- saccharides (one) Di- saccharides (two) Poly- saccharides (many)

• Monosaccharides (simple sugars of 3 to 6 carbons)

• Glucose C6H12O6 (‘blood sugar’)

• Fructose C6H12O6 (fruit)

• Ribose C5H10O5 (nucleic acids)

Carbohydrates• Disaccharides

• Composed of twomonosaccharides.

• Sucrose (table sugar)C12H22O11

Glucose + Fructose = Sucrose + water

Carbohydrates

• Polysaccharides (many) – long chains of monosacch.

• Starch – energy storage

• Cellulose – plant cell walls(wood, paper, cloth)

Function of Carbohydrates

• Energy storage (in the C-H bonds)

• For structure in plants (cellulose for cell wall)

• Carbon sources to make other molecules (nucleic acids, amino acids)

2. Lipids• Composed of C, O, H atoms• Fats and oils are made from two building

blocks: • Glycerol molecule

(hydrophilic;‘water loving’)

• Fatty Acids (hydrophobic;

‘water hating’)

Lipids• Fats are solid lipids at room temperature

(usually animal-derived: lard, butter)

• Oils are liquid lipids (usually plant-derived:

corn oil, peanut oil,

olive oil)

Lipids• Lipids DO NOT dissolve in water

• Phosholipids contain phosphorus

• The membranes of cells is a lipid bilayer

Function of Lipids• As a high-energy food• As part of cell membrane• As waxes, hormones, vitamins, pigments• Energy storage of lipids

– Monoglycerides (glycerol + 1 fatty acid chain)– Diglycerides (monoglyceride + 2nd fatty acid chain)– Triglycerides (diglyceride + 3rd fatty acid chain)

• Triglycerides = highest energy!

3. Proteins• Large complex molecules

• Composed of C, H, O, S and N

• Building blocks are amino acids (20)

Ribosome

protein

Function of Proteins• Building blocks of cells

• Transport: they help control

what passes through

Plasma Membrane

• Animal structure (hair, nails, tendons, muscles)

• Enzymes – to speed up chemical reactions

4. Nucleic Acids• Nucleic acids are large organic molecules

• Composed of C, H, O, P, N

• Basic unit is

the Nucleotide:

1) a sugar,

2) a phosphate, and

3) a nitrogenous base

Nucleic Acids• Nucleic acids are long chains of nucleotides

Examples

• DNA : Deoxyribonucleic acid,

carries information about the

entire cell

• RNA: ribonucleic acid, – a copy of DNA

Nucleic Acids: ATP• Another nucleotide compound is ATP, which has

a role of energy transfer/exchange (e.g. like an energy currency)

Function of Nucleotides: • Information storage (like a blueprint for the cell;

DNA, RNA)

• Energy carrier (ATP)

Life’s molecules• All life’s molecules share the following four

characteristics:

1. Carbon-based2. Formed from a few elements: C, H, O, N, P3. Modular construction – made from simple building

blocks1. Carbohydrates – monosaccharides (sugars)2. Lipids – fatty acids3. Proteins – amino acids4. Nucleic acids – nucleotides

4. Their shape and structure determines their function!

• Borrow one Textbook

• Also ordered a few textbooks on reserve at the Mckeldin Library

Raffle!

The plant cell

What is a cell?

• Basic building blocks of living organisms

• Form tissues and organs

• Each cell is functionally independent – it can live on its own under the right conditions– Uses sugars to get energy and stay alive– Contains all necessary info to replicate produce

a multicellular organism– Can make a whole plant from a single cell!

The Cell All plants are composed of cells.

• First discovered by

Robert Hooke in 1665

• Cell Theory:

1) Cell is the basic unit of life

2) Organisms are composed of cells

3) Cells arise from other cells

Two types of cells:• PROKARYOTIC

• EUKARYOTIC

Simple cells, lack organellesBacteria are prokaryotic10 to 100 times smaller than animal or plant cells

They have organelles: nuclei, mitoch., etc.Many multicellular organisms are eukaryotic:

Cells of plants, animals, fungi, are eukaryotic

Some unicellular organisms are eukaryotic: algae, amoeba, etc.

Prokaryotes EukaryotesOlder organisms (3.5 byo) More recent (1.5

byo)

Smaller 10 – 100 times bigger

No organelles Have organelles

THE PLANT CELL: Eukaryotic or prokaryotic?

EUKARYOTIC: HAS ORGANELLES!

Plant vs. animal cells

• Plant cells have 3 things animal cells don’t:

1) Cell walls

2) Vacuoles

3) Chloroplasts

Plant Cells• Structural building blocks

to form tissues and organs

• Plant cells: potentially can function independently.

Can even create a whole plant from a single cell (plant cloning)

THE PLANT CELL: outside

Outside: Cell wallPlasma membrane

Cell wall• Cell wall protects and supports cell

• Is made of CELLULOSE

• Allows water and other

molecules to

pass through

(like a cardboard box)

Primary vs. Secondary cell wall• Primary wall is formed early,

located on the outermost layer.

• Secondary wall is deposited on the inside, between Primary cell wall and

Plasma membrane.

• Middle lamella: what ‘glues’ adjacent cells together.

Cell membrane (or plasma membrane)

• Is a lipid bi-layer: hydrophilic “heads” (outer), hydrophobic “tails” (inside)

• Differentially permeable: Lets water pass through,

but not other molecules

Cell membrane (plasma membrane)

• Fluid Mosaic Model:

A double layer of phospholipids with scattered proteins…

(looks like “protein icebergs in a sea of lipids”)

Inside the Plant Cell:• Cytosol: a matrix of water (90%), proteins,

organic molecules, ions

• Cytoplasm: cytosol and organelles only

• Protoplast: all of the plant cell enclosed by the cell wall (plasma membrane, cytosol, organelles)

Cytoskeleton

• Microtubules & microfilaments: Make up the Cytoskeleton, a network of protein ‘cables’ that provide structure to the cell – they help in cell division & elongation.

• Important for mitosis

Plant Cell Organelles

• Organelles are membrane-bound sub-compartments within the cell.

• Each has its own function.1. Nucleus2. Mitochondria3. Chloroplast4. Vacuole5. Ribosomes6. Endoplasmic reticulum7. Golgi apparatus

Nucleus

Nucleus: contains all genetic information (DNA) in chromosomes.

Plant nucleus

• Chromosomes:DNA & proteins

• NucleolusBodies where ribosomes are made

MitochondriaMitochondria: Provides energy to cell by

converting sugars into chemical energy (respiration)

• “The powerhouse of the cell”

Parts of the Mitochondria

Chloroplasts

• Chloroplasts: Site for photosynthesis.

• Produce sugars from carbon dioxide, water and sunlight.

Parts of a chloroplast

Chloroplasts• Contain chlorophyll (makes the plant green)

Vacuole• Vacuole: Stores a watery solution of sugars,

salts, acids, proteins.

Vacuole

• Makes up to 90% of plant cell volume

• Makes cells turgid

• Has its own membrane, called tonoplast

vacuole

Vacuole contents

• Often acidic content (sap),

it’s what makes lemons and limes taste tart!

Ribosomes• Ribosomes: are the site for protein synthesis

• Use information contained in DNA to produce proteins.

• Not membrane bound.

Endoplasmic Reticulum (ER)

• Endoplasmic Reticulum (ER): a network of folded membranes throughout the cytoplasm

Endoplasmic Reticulum (ER)

Smooth ER: lacks ribosomes, used for packaging and transport of proteins, also to make lipids

Rough ER : has ribosomes for protein synthesis

Golgi apparatus• Golgi apparatus:

• A stack of flattened, hollow, membranous sacs

• Modifies proteins, lipids from the ER.

• Packages these materials in vessicles to the plasma membrane.

• “UPS of the cell”

Ribosomes, ER & Golgi in action:

The plant cell is like a “Chemical Factory”

Endosymbiont Theory

How did eukaryotic organisms evolve?

How did chloroplasts and mitochondria evolve?

Chloroplasts and mitochondria:

• Same size as bacteria

• Have their own DNA

• Divide similarly

Cyanobacteria Chloroplasts

Endosymbiont Theory (p.26, box 2.2)• Chloroplasts and Mitochondria are descendants

of once free-living prokaryotes that were engulfed by larger cells…

establishing a symbiotic (mutually beneficial) relationship.

THANKS!

Next week: Plant anatomy & physiology…

Have a great weekend!